The enteric nervous system mediates sphincteric reflexes, peristalsis and many other gut functions. Most intrinsic, enteric nerves contain peptide neurotransmitters. Our work determining neuropeptide sequences in the activation of the lower esophageal sphincter responses to acid and the pyloric responses to intraluminal nutrients suggests that Sphincteric reflexes are mediated by complex interactions of neuronpeptides. Altered peptide innervation may be responsible for disorders of intestinal motility. Further definition of the physiologic role for neuropeptides is limited by: the lack of studies that correlate structure and function; an inadequate understanding of the interactions between neuropeptides; an incomplete description of peptide innervation; and the lack of specific antagonists to peptide transmitters. This proposal will examine the role of the enteric nervous system in the control of the lower esophageal sphincter by correlating immunohistochemically-defined innervation with motility responses. Specifically, these studies will correlate the distribution, synaptic patterns and intensity of peptide immunoreactivity with the sphincteric responses to the synthetic peptides. We will continue to examine the interactions between enteric nerves, with special emphasis on studying nerves that show consistent patterns of synaptic interactions of co- localization by immunohistochemistry. Secondly, the local circuity of the enteric nerves will be defined using retrograde axonal transport markers, cholera toxin conjugates and lectinc. These techniques will also be used to define LES innervation by peptidergic nerves from adjacent organs and from sympathetic ganglia. Thirdly, we will continue to examine the sensitivity and specificity of nearly synthesized peptide antagonists to vasocative intestinal polypeptide and bombesin. Finally, we will examine the influence of chronic sympathetic denervation (immunologically and surgically induced) on neuropeptide immunoreactivity. The intracellular integrity of enteric nerves and their supporting stromal cells will be defined using immunohistochemistry of neurofilaments and glial filaments. In each study, anatomic features determined by immunochemistry or morphometry will be correlated with physiologic data so that a comprehensive understanding of the circuitary of the enteric nervous system can be achieved.